Process of making alkali cyanids.



BEST AVAILABLE COP UNITED STATES Patented April 18, 1905.

PATENT OFFICE.

PROCESS OF MAKING ALKALI CYANIDS.

SPECIFICATION forming part of Letters Patent No. 787,380, dated April 18, 1905 Application filed May 20, 1903. Serial No. 157,968.

To all whom it may concern:

Be it known that we, CHARLES B. JAooBs, a resident of Port Chester, in the county of Westchester, and ROBERT A. WITHERSPOON 5 and NATHANIEL THURLOW, residents of Niagara Falls, in the county of Niagara, State New York, citizens of the United States, have invented certain new and useful Improvements in Processes of Making Alkali o Cyanids, of which the following isa full and complete specification.

a Our invention relates to the manufacture of alkali cyanids. Its object is to produce a practically pure alkali cyanid from cyanamids or materials containing cyanamids, and more particularly the cyanamids of the alkalineearth metals.

; InLetters Patent of the United States Nos. 657,937 and 657,938, dated September 18, P 1900, and issued to Charles B. Jacobs, are l disclosed processes for the making of cyanids of the alkaline-earth metals for use as such or for conversion into the more commonly used cyanids of sodium or potassium. The yield v; of alkali cyanid which is obtained by these processes is diminished b reason of the presence of the cyanamid of t e alkaline earth, together with other impurities. The product obtained by carrying out these processes is found to consist approximately of twentyfive per cent. of barium cyanid and eighteen per cent. of barium cyanamid, together with a mixture of free carbon, barium oxid, a small proportion of barium carbid, some sulfids, and some ferrocyanid. compounds due to impurities in the coal. In the performance of this process hitherto great difficulty has been experienced in separating the barium cyanid from the other compounds present in The presence of barium thefurnaceproduct. cyanamid presents particular difficulty on account of its similarity in solubility in ordinary solvents to barium cyanid. The sulfid and ferrocyanid impurities also interfered with the efiiciency of the process bycontaminating the finished product. Furthermore,

CHARLES B. JACOBS, OF PORT CHESTER, AND ROBERT A. \VlTl-IERSPOON AND NATHANIEL THURLOW. OF NIAGARA FALLS, NEW YORK, ASSIGN- ORS, BY MESNE ASSIGNMENTS, TO CYANIDE COMPANY, OF JERSEY CITY, NEW JERSEY, CORPORATlON OF NEW JERSEY.

in the ordinary method of lixiviation of the product with a dilute solution of caustic soda or caustic potash the nitrogen fixed in the furnace as bariumcyanamid was a total loss, and it was-only the nitrogen which entered into the constitution of the barium cyanid which was utilized, since it was only the cyanid which was converted into the sodium or potassium cyanid, and this was contaminated by the cyanamid compound, which greatly interfered in the subsequent production of anhydrous sodium or potassium cyanid.

One of the objects of the present invention is to obviate such difficulties and objections in the processes above referred to and to eliminate the impurities in the finished product.

An important feature of the present invention consists in utilizing all of the nitro en fixed-in the furnace product, includin hat which enters into the constitution of the cyanamid, as well as that which enters into the constitution of the cyanid, and to utilize the whole of it in the formation of sodium or potassium cyanid.

Our process as applied to the productobtained by the patented processes above referred to consists in the following'steps: The furnace product such as is obtained on carrying out the processes disclosed in the before-mentioned Letters Patent and which consists of barium oxid, barium cyanid, barium cyanamid, free carbon, and such impurities as barium sulfid and barium carbid is analyzed to.ascertain the exact percentage of barium cyanid and barium cyan lowing equation:

sawsi2+BaoN,+o+2Na,oo,=4NaoN+2Baco,. In carrying out the process without reference to the patents herein mentioned and in working with cyanamids alone the reaction would appear as follows:

BaCN,+C+Na,CO =2NaCN+BaCO Instead of the sodium or potassium carbonate a mixture of sodium and potassium carbonates may be used if it be desired to produce the double cyanid of sodium and po tassium. Other suitable alkali compounds may be used instead of carbonate without departing from the invention. In any event it is only necessary to mix the proper amount of alkali carbonate with the furnace product and to thoroughly incorporate the mixture. The mixture is then introduced into a closed retort or covered crucible'and brought to a red heat, whereupon the reaction illustrated above takes place and the nitrogen compounds of barium are converted without loss of nitrogen into the alkali cyanid.

The carbon necessary to convert the cyanamid compound into the cyanid may in some cases be the residualfree carbon in the furnace product; but as thiscarbon, owing to the extreme heat to which it has been subjected in the electric furnace, is frequently partially gra hitized, and therefore less active chemica ly than ordinary carbon, it is preferable to add free carbon to the charge in the form of powdered charcoal.

' The following is given as an illustrative example of the commercial application of the process for treating one ton of furnace product containing twenty-five per cent. of barium cyanid and elghteen per cent. of barium cyanamid: two thousand pounds furnace product, (containing approximately five hundred pounds Ba(CN) and approximately three hundred and sixty pounds BaCN2,) five hundred and six pounds carbonate of soda, fifty pounds ground charcoal. The above charge is thoroughly ground and mixed and then placed in a closed fusion pot or crucible and raised by external heating to a red heat. The reaction before stated takes place, and approximately four hundred and fifty-eight ounds of sodium cyanid are formed in the used mass. After cooling the fused mass is ground and lixiviated with water. The resulting solution contains from eight per cent. to a maximum of twenty per cent. of so dium cyanid, depending upon the uantity of water used in lixiviation. The so ution also contains barium hydrate, due to the action of water on the barium oxid and barium car- BEST AVAlLABLE COP bid present in the furnace product, some ferrocyanid, and some sulfid compounds. The solution is freed from the barium compounds by precipitation of the barium as a carbonate by treatment with bicarbonate of soda. This results in the introduction of sodium hydrate into the solution in place of the barium salts. The solution is now concentrated in vacuo until it contains thirty-five to fifty per cent. of sodium cyanid. When concentrated, the specific gravity varies from 1.26 to 1.37 varying with the amount of impurities present. The concentrated solution is now cooled -to 20 centigrade, when the small amount of ferrocyanid compounds settle out and are filtered off. The solution is now cooled as low as ossible. At a temperature of 5 centigra e a or stallized cyanid of sodium, NaCN +2H (known to .Watt; see Watts Chem. Diet, Vol. 2, page 347) begins to separate out of the solution, and the separation of pure crystals continues even when the temperature is lowered to 17 centigrade. These crystals are drained and centrifugated to free them from the mother li uor which contains the impurities originiilly present in the solution and some so dium cyanid, The mother-liquor is reconcentrated and a second crop of crystals of sodium cyanid thus obtained. These crystals are not so ure as the first crop and are therefore added to the next lixiviation liquor obtained from a new batch of furnace product after the liquor has been freed from barium salts in the usual manner. From this liquor the alkali cyanid is recovered pure in a manner similar to that described above for the first crop of crystals. Since the impure second crop of crystals remains practically constant and is always obtained in the above-described manner, there is no tendency for the sodium hydrate and sodium sulfid to separate from the lixiviation solution with the first crop of crystals even when the temperature is as low as 17 centigrade. By the abovedescribed process there is therefore obtained only pure crystallized cyanid of sodium. These first crystals so obtained having been freed from the mother-liquor are placed in a vacuum-pan and the water of crystallization driven off, with the result that there is thus obtained pure anhydrous cyanid of sodiumor otassium.

While we have escribed the present process as applied to the furnace product obtained as a result of the processes disclosed in the Letters Patent herein referred to, we desire it to be understood that our present process is not to be restricted to treatment of that product only, but that'it may be employed for obtaining in a similar manner pure alkali cyanid from materials comprising the cyanids of BEST AVAILABLE COP the alkaline earths, together with the cyanamids of the alkaline earths, or from cyanamids alone.

Having thus described our invention, what we claim as new, and desire to protect by Letters Patent, is

1. The process of obtaining alkali cyanid which consists in reactin upon alkalineearth cyanids or cyanami s with an alkali :ompound, forming a solution of the product of such reaction, cooling said solution to a temperature where the alkali cyanid formed separates out leaving the impurities in the sowution.

2. The process ofobtaining alkali cyanid which consists in reacting upon alkaline :arth cyanids or cyanamids with an alkali :ompound forming a solution of the product )f such reaction, cooling said solution to a ;emperature of 5 centigrade or lower to sepa ate out the alkali cyanid formed, leaving the mpurities in the solution.

3. The process of obtaining alkali cyanid, vhich consists in reacting u on a cyanamid vith an alkali, forming a so ution of the retction mass, concentrating and cooling said :olution to a point where the alkali cyanid ormed separates out leaving the impurities n" solution.

4. The process of obtaining aklali cyanid, vhich consists in reacting upon a mass conaining alkaline-earth cyanids and cyananids with an alkaline carbonate to convert he cyanids and cyanamids into alkali cy'alldS, forming a solution of the reaction mass,

' }ooling the solution so obtained, whereby the ilkali cyanid resulting from the reaction sep aiates out leaving the impurities in the soluion, then separating the alkali cyanid from "he solution.

5. The process of obtaining alkali cyanid, rhich consists in reacting upon a mass conaining alkaline-earth cyanids and cyanaiids and carbon with an alkaline carbonate, arming a solution of the reaction mass, conentrating and coolin the solution so obained,'whereby the a kali cyanid resulting tom the reaction separates out leaving the npurities in the solution, and then separatlg the alkali cyanid from the solution.

6. The process of obtaining alkali cyanid, 'hicli consists in reacting upon a mass coniining alkaline-earth cyanids and cyanalldS with an alkaline carbonate, forming a )lution of the reaction mass, coolin the soltion so obtained, whereby the alkaTi cyanid sulting from the reaction se arates out aving the impurities intthe so ution, then aparating the alkali cyanid from the soluon, reconcentrating said solution containg the impurities until a further quantity of .kali cyanid separates out, adding the crystals so obtained to a fresh quantity of lixiviated solution of the reaction mass, concentrating this solution, cooling the same, filtering, and again cooling until sodium cyanid separates out.

'7. The process substantially as herein described of treating a mixture of alkaline earth cyanids and cyanamids with a fixed alkali carbonate at a red heat, thereby obtaining the fixed alkali cyanids, forming a solution of this in water together with the soluble impurities present, concentrating and cooling this solution to a point at which only cyanid of the alkali metal separates out leaving the impurities in solution.

8. The process of obtaining alkali cyanid, which consists in treating a mixture of alkaline-earth cyanids and cyanamids with afixed alkali carbonate at a red heat, thereby 0btaining the fixed alkali cyanids, forming a solution of this in water together with the soluble impurities present, removing from said solution the substances which are less soluble than the alkali cyanids to be produced, by precipitation of said substances with a reagent which leaves in the solution roducts of greater solubility than the said a kali cyanids, concentrating and cooling this solution to a point at which only cyanid of the alkali metal separates out leaving the impurities in solution.

9. The process of obtaining alkali cyanid, which consists in reacting u on a mass containing alkaline-earth cyani s and cyanamids with an alkaline carbonate to convert the cyanids and cyanamids into alkali cyanids, formin a solution of the reaction mass, treatin said solution with a precipitant for the alka ine-earth compounds present, removing said precipitate, concentrating and cooling the solution to a point where only the alkali cyanid separates out leaving theimpurities in solution.

10. The process of obtaining alkalic anid, which consists in treating a mixture 0 alkaline-earth cyanids and cyanamids with a fixed I alkali carbonate at a red heat, thereby obtaining the fixed alkali cyanids, forming a solution of this in water together with the soluble impurities present, treating said solution with sodium bicarbonate, removing the recipitate formed, concentratin and coo in the solution to a oint at whic only cyani of an alkali meta separates out leaving the impurities in solution.

11. The process which consists in treating a mixture of alkaline-earth cyanid-and cyanamid with an alkali carbonate, heating the I mass to a temperature to convert the cyanid and cyanamid to alkali cyanid, lixiviating the mass, preci itating from the solution so obtainedtheIa kaline-earth compounds present,

BEST AVAILABLE GOP and concentrating and cooling the solution to a point where only the alkali cyanid separates out leaving the impurities in solution.

12. The process which consists in treating A a mixture of alkaline-earth cyanid and cyanamid with an alkali carbonate, heating the mass to a temperature to convert the cyanid and cyanamid to alkali cyanid, lixiviating the mass. precipitating from the solution so ob tained the alkaline-earth com ounds, and concentrating and cooling the so ution to precipitate some of the impurities, removing said impurities, then further concentratin and cooling the solution to a point where on y the alkali cyanid separates out, leaving the remaining impurities in solution.

CHARLES B. JACOBS. R. A. WITHERSPOON. NATHANIEL THURLOW. Witnesses for Chas. B. Jacobs: HENRY C. WORKMAN, J GREEN. Witnesses for R. A. Witherspoon:

WM. C. l VALLACE, J. C. ROBERTS. Witnesses for Nathaniel Thurlow: FRANK T. TI-IURLOW, i HENRY C. WORKMAN. 

